In existing multilateral completions where a junction is located to provide access to a lateral and the main bore and a diverter is used to control the access. Typically an initial diverter is run into the junction to provide access to the main or lateral bore. The diverter in effect isolates the other of the bores so that the bore oriented for flow through the diverter is treated first. The top string is installed to isolate the casing above the junction. The top string must be removed to pull the first diverter and a second diverter with an orientation for the bore that has yet to be treated is run in. The top string is then reinstalled. At that point the other bore is treated.
The disadvantage of this system is the multiple trips with the top string to switch diverters. The present invention addresses the extra trip issue with a diverter that is small enough to come through the top string without having to remove the top string. Of course, moving the diverter through the top string puts a size limit on a diverter which also limits the drift dimension through the diverter. This can have an adverse effect on the number of fracturing stages that can be pumped during the treatment. To offset this effect the treatment bottom hole assembly that typically has multiple valves that have different size ball seats that increase in size as the treatment moves uphole is instead configured with a system where the ball seats on a collection of sleeves operate on a single ball size. This alleviates the negative affect of limiting the number of fracturing stages. While fracturing sleeve arrangements that operate with a single ball size are known in single boreholes with no laterals as shown in US 2013/0043043, such systems have never been used in multilateral applications and not in applications where the isolation of pressures across the junction is completed. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.